21661880457 has 24 divisors (see below), whose sum is σ = 33924236736. Its totient is φ = 12258031968.

The previous prime is 21661880389. The next prime is 21661880489. The reversal of 21661880457 is 75408816612.

It is not a de Polignac number, because 21661880457 - 2⁷ = 21661880329 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21661880057) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 700198 + ... + 730479.

It is an arithmetic number, because the mean of its divisors is an integer number (1413509864).

Almost surely, 2^21661880457 is an apocalyptic number.

It is an amenable number.

21661880457 is a deficient number, since it is larger than the sum of its proper divisors (12262356279).

21661880457 is a wasteful number, since it uses less digits than its factorization.

21661880457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1430797 (or 1430790 counting only the distinct ones).

The product of its (nonzero) digits is 645120, while the sum is 48.

The spelling of 21661880457 in words is "twenty-one billion, six hundred sixty-one million, eight hundred eighty thousand, four hundred fifty-seven".